Method of drying finely-divided materials



Feb. 16 1926. I I 1,573573 J. B. BRONSTEIIN METHOD OF DRYING FINELYDIVIDED MATERIALS Filed Oct. 25, 1919 Im 75 Jpssafi. Bram 5&3

WM rum Patented Feb. 16, il2@.

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JESSE B. BRONS'IEIN, 9F ALLEN'IOWN, PENNSYLVANIA, ASSIGNOE IOi TRGJANPOW- DER GQMPANY, OF NEW YORK, N. 1 A CORPDBATION OF NEW YORK.

METHOD F DRYING FINELY-DIVIDED MATERIALS.

Application filed october 23, 1919. Serial No. 332,714.

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Be it known that I, Jesse B. Bnoss'rnm, a citizen of the United States,and resident of Allentown, Lehigh County, Pennsylvania, have inventedcertain Improvements in Methods of- Drying Finely-Divided Materials, ofwhich the following is a specification.

This invention relates to processes of drying solid explosive bodies,and relates more particularly to an improved process for drying wetnitro starch. trinitrophenylmethylnitramine and similar highly sensitiveexplosives existing in a finely divided state.

The attached drawing illustrates in perspective apparatus by means ofwhich my method may be utilized.

The usual practice in drying nitrostarch,

trinitrophenylmethylnitramine, tetranitroaniline and other likepulverulent and highly sensitive explosive bodies has been to spread thewet material upon trays in a thin layer, the trays being spaced apartand then exposed to warm air or other drying means.

This method, however, is open to the objection that as the materialbecomes dry,

particles thereof are carried from the trays by the circulating aircurrents and deposited upon the shelves or racks supporting the trays,and there is always danger that friction produced by the movement of thetrays in andout of their positions on the racks may ignite theseparticles. This process is open to further objection becauseof thestatic electric charges which may be produced by the passage of the warmair over and between the parallel'layers of the drying material and theseparation of the small particles from the body of the material asalready explained, these electric charges undoubtedly being responsiblefor some of the numerous accidents which occur under this system.

I have discovered a means whereby these objectionable features may beeliminated, and the drying process for explosive materials of the naturespecified made comparatively safe. My improved process com- 50 prisesbroadly, separating the material to be dried from the drying agent bymeans of a fabric or the like which is impermeable to the drying agentand to the solid tobe dried, but which is permeable to the liquid fromwhich the solid is to be separated, and 111 thus drying the finelydivided explosive substance by capillary transfer of its con-.

tained liquid to the fabric surface, instead of permitting the air orother drying fluid to come into direct contact with any free surface ofthe material to be dried.

In the accompanying drawing I have shown, in perspective, a convenientform of apparatus, by means of which the method may be employed; saidapparatus comprising rail 1 supported by any suitable means (not shown)in a suitable drying room or tunnel, on which rail is hung a movablesupport 2 carrying hooks 3 adapted to receive and support the dryingbags or tubes 4.

In carrying out my process I prefer to enclose the wet explosivematerial in containers COIlSiStlIlg of elongated tubular bags 4 of aclosely woven fabric of silk, wool, or cotton, the fabric beingsufficiently close to prevent particles of the contained material frompassing through, but not so tight as to prevent the ready passage of thewater or other liquid from which the finely divided solid is to befreed. A convenient size of tube for the purpose is fifty inches inlength, and from one and one-half inches to two and one-half inches indiameter, though of course I may employ tubes of any size, thedimensions being varied to suit existing conditions.

In passing the wet explosive material into I the tubes, I prefer to addto the material sufficient water to form a fluid or semi-fluid mass,this mass being of a consistency to permit of it being poured into thebags, this method of loading having been found simple and cheap. Havingtransferred the wet ma terial to be dried to the interior of theelongated fabric containers, I next preferably hang a number of thesefilled containers from hooks 3 in a suitably ventilated room or chamber.The tubes may be hung in any manner desired, but I prefer to hang themfrom one extremity from hooks or supports spaced from three to twelveinches apart, in a cham- I her or tunnel only slightly deeper than thelength of the tubes, and of width 'suflicient to accomodate the numberof tubes forming a single row, the length of the tunnel being asdesired. WVarm air is then passed through the chamber, the temperatureof the air being preferably about 60 C. After the bags have been filledsuflicient time is preferably allowed for the excess water to-drain off,the fabric of the bag acting as a filtering surface. The wet bags arethen hung in the drying chamber or tunnel, previously described, wherethe moisture in the material in the interior of the tubes istransferredwholly by capillarity to the surface of the tube, this cloth surface ofthe tube continually losing its moisture to the air current. As thefabric surface of the tube becomes dryer, it in turn takes up water bycapillarity from the layer of the explosive material in contact with it,and this layer in turn abstracts Water from the next inner layer.

This transfer of water by capillarity continues until, at the expirationof from 24 to 48 hours, with proper drying conditions, the entire tubeand contents are substantially dry- I claim:

1. The process of drying finely divided solids, which comprisesconfining the material to be dried in a tubular fabric container 25 oflength relatively great as compared to its Width, and exposing saidcontainer to a drying atmosphere. p

2. The process of drying finely divided solids, which comprisesconfining the material to be dried in a tubular fabric container oflength relatively great as compared to its Width, and suspending saidcontainer with its contents in a current of drying fluid.

3. The process of drying finely divided solids, which comprises theforming of said solid into a fluid mass by admixture with a liquid,causing said mass to flow into a tubular fabric container of lengthrelatively great as compared to its Width, and exposing said containerto a current of drying fluid.

4. The process of drying nitrostarch, which comprises filling a tubularfabric bag of length relatively great as compared to its Width with aslurry of the nitrostarch, and exposing the bag to a drying atmosphereuntil the evaporation of the moisture from the surface of the bag hasreduced by capillarity the moisture content of the contained nitrostarchto the desired extent.

JESSE B. BRONSTEIN.

